In a process referred to as quorum sensing, bacteria communicate using chemical signaling molecules called autoinducers. By monitoring increases and decreases in autoinducer concentration, quorum-sensing bacteria track changes in cell-population density and synchronously switch into and out of group behaviors. Quorum sensing allows bacteria to collectively carry out tasks that would be unsuccessful if carried out by an individual bacterium acting alone.
Both Gram-positive and Gram-negative infectious bacteria, which include human, animal, plant, and marine pathogens, use quorum sensing strategies to control virulence. Quorum sensing also controls biofilm formation. Biofilms are communities of bacterial cells adhered to surfaces and encased in a self-excreted matrix of extracellular polymeric substances. In most environments, bacteria are found predominantly in biofilms. These biofilms are also widespread in industrial systems and are associated with increased risk of infection when found in clinical environments and in indwelling medical devices. These bacterial communities can cause chronic infections in humans by colonizing, for example, medical implants, heart valves, or lungs. Staphylococcus aureus, a notorious human pathogen, causes some of the most common biofilm-related infections. In these environments, biofilms are highly problematic. Bacteria in biofilms are often significantly more resistant to antibiotics and antimicrobial agents. Thus, they can be very difficult to eradicate.
In settings involving flow across the biofilm, as in rivers or in all manners of industrial and medical fluid handling systems, filamentous biofilms, called streamers, can be formed. These streamers can have a dramatic effect on the biofilm environment. In rivers, for example, the biofilm streamers can increase transient storage and cycling of nutrients and can enhance the retention of suspended particles. In industrial settings, the biofilm streamers have been associated with increased issues associated with clogging and pressure drops. Although biofilms and streamers play such an important role in industrial and clinical settings, the precise mechanisms driving their formation are poorly understood. This underscores the need for a system that mimics natural formation processes and allows for screening of potential inhibitors of biofilm and biostream formation.
Additionally, bacterial infections are treated with bactericidal or bacteriostatic molecules that impede four major processes: DNA replication, transcription, translation or tetrahydrofolic acid synthesis. Existing methods for treating bacterial infection unfortunately exacerbate the growing antibiotic resistance problem because they inherently select for growth of bacteria that in turn can resist the drug. What is needed are new methods of screening for treatments that avoid selecting for drug resistant bacteria.